Lead-in seal for evacuated envelope of an electron discharge device for connecting electrodes located within said envelope to a voltage source positioned outside said envelope



p 27, 1966 w. H. WILBANKS LEAD-IN SEAL FOR EVACUATED ENVELOEE OF AN ELECTRON DISCHARGE DEVICE FOR CONNECTING ELECTRODES LOCATED WITHIN SAID ENVELOPE TO A VOLTAGE SOURCE POSITIONED OUTSIDE SAID ENVELOPE Filed Feb. 27, 1965 I I I I I I I f 1 W/LL/AM H. W/LBANKS Fig. 2

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BUG/(HORN, BLORE,,KLAROU/$T 8 SPAR/(MAN ATTORNEYS United States. Patent LEAD-IN SEAL FOR EVACUATED ENVELOPE OF AN ELECTRON DISCHARGE DEVICE FOR CON- NECTING ELECTRODES LOCATED WITHIN SAID ENVELOPE TO A VOLTAGE SOURCE PO- SITIONED OUTSIDE SAID ENVELOPE William H. Wilbanks, Hillsboro, Oreg., assignor to Tektronix, Inc., Beaverton, Oreg., a corporation of Oregon Filed Feb. 27, 1963, Ser. No. 261,443. 9 Claims. (Cl. 313317) The subject matter of the present invention relates generally to insulating seals having electrical leads extending therethrough, and in particular to lead-in seals in which the electrical lead is formed by a light transparent, electrically conductive coating of tin oxide or other suitable material which is provided on the surfaceof one of the members to be joined together.

The lead-in seal of the present invention is especially useful when employed in the evacuated envelope of an electron discharge device in order to connect an electrode located within such envelope to a voltage source or other electrical circuit positioned outside of such envelope. In the preferred embodiment of the present invention a tin oxide coating is applied to the inner surface of the glass face plate of the envelope of a cathode ray storage tube, and extends through a glass frit seal joining such face plate to a ceramic funnel shaped envelope portion so that the tin oxide coating formsan electrode within the tube envelope and also functions as a lead connecting this electrode to the exterior of the envelope. The transparent, conductive coating of tin oxide is covered by a layer of phosphor material having a thickness Within the critical range of thicknesses over which such phosphor layer is capable of storing bistable charge images for an indefinite controllable time so that the tin oxide coating and phosphor layer form a direct viewing,'bistable storage target. A storage tube employing this type of target is shown in copending United States Patent 3,214,631 entitled Storage Tube Having Store and/or Non-Store Sections, filed August 6, 1962, by Robert H. Anderson. The envelope structure of this storage tube is disclosed in copending United States Patent 3,207,936, entitled, Electron Beam Display Device, which was filed on August 21, 1961, by William H. Wilbanks et al. However, it should be understood that the lead-in seal of the present invention may be employed in conventional cathode ray tubes which do not store, as well as in other electron discharge devices.

The lead-in seal of the present invention has several advantages over conventionallead-in seals including those which employ a metal pin, ring or other member as the electrical lead extending through an insulative seal since these latter seals are more subject to breakage due to thermal expansion of the metal lead member .or to the mechanical force of a blow accidentally striking such projecting lead member. Another advantageof the present lead-in seal is that it may be made by a method which is simple and inexpensive to carry out compared to conventional methods, and the resulting lead-in seal structure produced thereby is simple, rugged and reliable. The use of a thin, conductive coating of tin oxide as an electrical lead extending through a glass seal allows a great number of similar leads to extend through the same seals since the conductive coatings may be positioned extremely close together so that they are separated only by small gaps to insulatingly space such leads fromeach other. A further advantage of the lead-in seal of the present invention is that it may be formed at the same time as the electrode to which it is connected inside the envelope, merely by making such electrode and such lead as different portions of the same tin oxide coating. This eliminates the necessity of providing a separate connection between the lead "ice and the electrode, which would require additional manufacturing time and could be subject to failure. While the new lead-in seal may be employed between two glass members, it may also be used to joint dissimilar materials such as glass to ceramic, glass to metal, or ceramic to metal. However, in the case when a metal member is joined to an insulative member, the transparent, conduc tive tin oxide coating would always be applied to the insulative member so that it is insulated from the metal member by the sealing material.

It is therefore, one object of the present invention to provide an improved lead-in seal structure and method of forming such seal structure.

Another object of the present invention is to provide an improved lead-in seal which employs a tin oxide coating as the electrical lead so that such seal is not subject to breakage.

A further object of the present invention is to provide an improved lead-in seal that may be formed by a method of manufacture which is simple and inexpensive.

A still further object is to provide an improved leadin seal having a plurality of electrical leads extending through the same seal.

An additional object of the invention is to provide an improved lead-in seal for the envelope of a cathode ray storage tube in which a plurality of insulatingly spaced, light transparent, conductive coatings of tin oxide are provided on the glass face plate of such envelope so that they extend through the same glass seal joining such face plate to the funnel portion of such envelope and connect a plurality of storage target electrodes within such envelope to difierent voltage sources exterior of the envelope.

Still another object of the invention is to provide an improved lead-in seal for adjoining members made of glass and ceramic or other dissimilar materials.

A still further object of the present invention is to provide an improved lead-in seal in which a tin oxide coating is employed as the electrical lead as well as the electrode connected to said lead. Other objects and advantages of the present invention will be apparent from the following detailed description of a preferred embodiment thereof and from the attached drawings of which FIGURE 1 is a side view of a cathode ray storage tube empolying one embodiment of the lead-in seal of the present invention; and

FIGURE 2 is a horizontal section view taken along the line 22 of FIG. 1 showing an enlarged view of a portion of the lead-in seal and envelope structure of the present invention.

The envelope structure of the cathode ray tube shown in FIGS. 1 and 2 is similar to that shown in copending United States Patent 3,207,936, mentioned previously. Thus, the envelope may include a flat, light transparent, rectangular glass face plate 10 which is sealed to the large rectangular end of a hollow, ceramic funnel member 12 by the lead-in seal of FIG. 2 in a manner hereafter described. The small circular end of the funnel member 12 may be sealed to a hollow, cylindrical neck member 14 of glass similar to that of face plate 10 by means of an annular seal 16 of a suitable glass frit of the same material employed in the lead-in seal. 7

An electron gun structure (not shown) may be positioned within the neck member 14 which functions as the writing gun of the storage tube and is connected to the exterior of the envelope by means of metal pins 18 extending through the side of such neck member and metal pins 20 extending through the rear end of the neck member. The pins 20 are held in spaced, insulated relationship by extending through the base of a socket member 22 made of a suitable plastic material which is cemented or targetvoltages forthe phosphor layer.

ductive coating 24 is connected to such a target voltage,

isolation shield between such deflection plates, while the :base pins 20 are connected to the remaining electrodes in the writing, gun as well as to other electrodes in additional electron guns (not shown) positioned inside funnel member 12 which function as flood guns. This storage tube may be similar to that shown in copending United States Patent 3,214,631, referred to above.

As shown in FIG. 2, the face plate may be provided with a light transparent, electrically conductive coating 24 of tin oxide or other suitable conductive material over the inner surface of such face plate. This tinoxide coating may be covered by a layer of phosphor material 26 over that portion of the conductive coating which exists inside the funnel 12 of the envelope. This phosphor layer 26 has a thickness within a critical range of thicknesses'over which the posphor materialwill store a bistable charge image for an indefinite controllable time. Thus the phosphor layer 26 and tin oxide coating24 form a direct viewing, bistable storage target as described in detail in the copending Patent 3,214,631 previously referred to. In

order to enable the phosphor layer 26 to operate as a bistable storage dielectric, the tin oxide coating 24 beneath .such phosphor layer must be connected to a suitable source of quiescent D.C. voltage within the stable range .of

When the conthe phosphor layer 26 will store a bistable charge image produced or such phosphor layer by the writing gun and maintained by the flood gun. A light image is emitted by the phosphor layer 26 corresponding to the charge image,

which is observed through the face plate 10 and the conductive coating 24 in the manner of a conventional cathode ray tube so that the tin oxide coating must be light trans-v parent.

A graticule scale may be provided on the inner surface of the face plate 10 including a pluralityof horizontal and vertical intersecting graticule linesv 28 which may be formed of glass frit deposited on the inner surface of such face plate, in order to measure the voltage and timechar acteristics of the wave form stored on the phosphor layer 26. This graticule scale maybe edge lighted in the manner shown in copending Patent 3,207,936. Also a wall coating electrode 30 of silver or other conductive material may be provided on the inner surface of the ceramic fun nel member 12 adjacent the. storage target in order to collimate the flood electrons so that they strike the phosphor layer 26 substantially at right angles thereto, and to at least partially collect the secondary electrons emitted from the phosphor layer due to the bombardment of such velope by extending such conductive coating through an annular glass seal 32 joining the, funnel member 12 to the. face plate 10. A lead strip 34 of silver paint or other conductive' material may be provided over the outer surface of the funnel member 12 and electrically connected to the tin oxide coating 24 by a connector 36 of silver .solder.

so that a DC. voltage may be applied to the target elec trode 24 through the lead strip at a position remote from [the face plate. The lead strip 34 is electrically connected,

to the lead portion 38 of the tin oxide coating 24 extending through the glass seal 32 to the outer edge of the face plate. The glass seal 32 may be formed from a glass frit material containing either devitrifiable glass or :undevitrifiable glass, as disclosed in copending United States Patent 3,207,936, whose thermal coefficient of expansion is substantially the sameasfthat of the ceramic material. used in funnel member 12 and the glass material in face plate 10 over a wide range of temperatures. Thus, the, glass seal 32 joins the annular edge of the large end of funnel member 12 to a portion of the inner surface of the, a face plate 10 adjacent its outer'edge with a vacuumtight" seal in the shape of a rectangular ring. The tin oxide coating 24 is actually composed of several oxides including stannous oxide (smo and stannic oxide (SnO), as well as conductive impurities such as tin fluoride and tin chloride. Thus the term .tin oxide coatingis hereby defined as including these compounds, although it consists predominantly of stannous oxide.

As shown in FIG. 1, a plurality of ditferent lead SlII'iPSl 34 may be provided in order to connect a plurality of separate insulated tin oxide coatings 24 on the inner surface of the face plate 10 to sources of different DC. voltage so that the wave form display portions of the phosphor layer 26 overlying such conductive coatings may be operated either in a storage or a non-storagemode depending upon the target voltage applied to such conductive coatings. This also enables the storage target to display the switch positions controlling the vertical gain and horizontal sweep speed of the Writing gun by forming some ofv the tin oxide coatings in the shape of number and letter characters, as is more fully described in copending United StatesPatent 3,214,631.

The transparent, conductive tin oxide coating 24 may be applied to the. face plate 10 in a conventional-manner including the step of first cleaning theglass plate with an alkali detergent or suitable, acid to remove dirt and suitable high temperature, without melting the glass of such face plate. Then the heated face plate issprayed in an oxidizing atmosphere such as air with a solution containing 17 to 20 grams of anhydrous stannic chloride (SnCl grams of methanol (CH OH), and .6 gram ammonium hydrogen fluoride ,(NH HF The stannic chloride largely. decomposes when heated by con-l tact with the heated plate and the tin oxidizes to. produce a tin oxide coating of predominately stannous oxide.- The ammonium hydrogen fluoride reacts with the tin com pound to produce a small amount: of tin fluoride to in-. crease the conductivity of the resultant tin oxide coating. The methanol is a solvent for the ammonium bifluoride and stannic chloride andvaporizes during heating: It

should be understood thatthis solution is only one example of many possiblesolutions which are well known in the tin oxide coating art. For example, ethanol may be used .as the solvent in place of methanol, and stannous chloride or another tin salt may be employed in placeof stannic chloride. This solution is sprayed by an air atomizer for 20 or, 30 seconds onto the heated glass plate While such plate remains in the oven. Then the coated face plate is cooled in the oven ata fast rate to room temperaturewhile being careful to avoid thermal shock to the glassplate. 'In order ;.to provide a particularlyj thick tin, oxide coating, the heating, spraying and cooling steps may 'be repeated.

. It has been found that a coating thickness between 1000 I and 5000 Angstroms will give the desired characteristics of good electricalconductivity and light transparency to 1 tween 100 and 2000 ohms per unit square. However, if should be noted that extremely thick coatingsoftin oxide will prevent the glass seal 32 from properly joining the face plate 10 to the funnel-member.

After the glass face plate has been provided with the tin oxide coating 24, a layer of glass frit may be provided on a portion of the face plate over the tin oxide coating in the region adjacent to but spaced from the outer edge of the face plate so that such coating extends through such layer. Thus the glass frit layer conforms to the annular shape of the large end of the ceramic funnel member 12. The tunnel member is then placed onto the glass face plate in-contact with the glass frit layer so that such glass frit is positioned between such funnel member and such face plate with the conductive coating 24 extending from the inside to the outside of such funnel member. Next this combination of the funnel member, glass frit layer and tin oxide coated face plate are subjected to a heat of about 450 C. for approximately 60 minutes to fuse the glass frit. The heating rate may be between 10 and C. per minute from room temperature to 450 C. which is the sealing temperature of the galss frit and is considerably above the incipient softening temperature of such glass frit, but below that of the glass face plae 10 and the ceramic member 12. Finally the members are cooled from 450 C. to room temperature at a rate of between 3 and 15 C. per minute to form the vacuum tight glass seal 32 between the funnel member 12 and the coated face plate 10. While it is not entirely clear how this seal is joined, it is believed that the conductive coating 24 extending through such seal is sufiiciently porous to allow the glass frit to penetrate through such coating to the surface of the face plate so that the seal is made to the face plate, rather than to the tin oxide coating.

It should be noted that various combinations of materials maybe employed for the ceramic funnel member 12, the glass face plate 10 and the glass seal 32. As disclosed in copending United States patent application Serial No. 132,915 now Patent No. 3,207,936, one suitable glass-ceramic system may be a funnel member 12 of fosterite ceramic having a composition by weight of approximately 28% magnesia 60% talc and 12%'k0a1in; a face plate 10 of soda lime glasshaving a composition by weight of 73.6% SiO ,'16% Na O, 0.6% K 0, 5.2% CaO, 3.6% MgO, and 1% A1 0 a seal 32 of devitrified glass. The devitrifiable glass frit material employed for seal 32 may be one of the lead-zinc 'borate type glasses disclosed in United States Patent No. 2,889,952 which issued to S. A. Claypoole on June 9, 1959, for Composite Article and Method. This devitrifiable glass is commercially available from Corning Glass Works of Coming, New York as Pyroceram Cement No. 7572.

It should be obvious to those having ordinary skill in the art that various changes may be made in the details of the above-described preferred embodiment of the present invention without departing from the spirit of the invention. For example, the ceramic funnel member 12 may also be provided with a tin oxide coating across the outer edge of its large end beneath the glass seal 32, which extends into contact with the wall coating 30 so that such wall coating may be connected to a source of electrical potential outside of the envelope by connecting such tin oxide coating to one of the lead strips 34. If this were done the tin oxide coating electrically connected to the wall coating 30 would be insulated from the tin oxide coating 24 by the glass seal 32 so that the wall coating 30 and the target electrode coating 24 could be connected to different D.C. voltages. For this reason, the scope of the present invention should only be determined by the following claims.

I claim:

1. An electrical connector structure, comprising:

a first body of electrical insulative material;

a second body of electrical insulative material;

a sealing layer of electrical insulative glass material having a thermal coefiicient of expansion similar to the materials of said bodies, said sealing layer being 6 fused directly to said first body and sealing said first body to said second body by a vacuum-tight seal; and a thin layer of electrically conductive material coated over .at least a portion of said second body beneath said sealing layer and extending from one side to the other of the seal so that electrical signals can be transmitted through said seal by said conductive ayer. An electrical connector structure, comprising:

first body of electrical insulative material; second body of electrical insulative material, one of said bodies being of ceramic and the other of glass; a sealing layer of electrical insulative glass material having a thermal coeflicient of expansion similar to the materials of said bodies, said sealing layer being fused directly to said first body and sealing said first bocdly to said second body by a vacuum-tight seal; an a thin layer of electrically conductive oxide coated over at least a portion of said second body beneath said sealing layer and extending from one side to the other of the seal so that electrical signals can-be Transmitted through said seal by said conductive ayer. 3. An envelope structure from an electron tube comprising: 1

a first envelope portion of electrical insulative material; a second envelope portion of electrical insulative materia a sealing layer of electrical insulative vitreous material having a thermal coeflicient of expansion similar to the insulative materials of said envelope portions, said sealing layer being directly fused to said first portion and sealing said first portion to said second portion by a vacuum-tight seal; and

a thin layer of electrically conductive material coated over at least part of the inner surface of said second portion and extending through the vitreous seal to the exterior of the envelope so that electrical signals can be transmitted through said seal by said conductive layer.

4. A lead-in structure for an electron tube, comprising:

a first envelope portion of ceramic material;

a second envelope portion of glass material;

a seal layer of electrical insulative glass material having a thermal coeificient of expansion similar to the materials of said envelope portions, joining said first lporltron to said second portion by a vacuum-tight sea a thin electrically conductive layer coated over at least part of the inner surface of said second envelope portion beneath said seal layer and extending through said seal; and

a connector layer of conductive material coated on the outer surface of said first envelope portion and the seal layer into contact with the conductive layer so that electrical signals can be transmitted through said seal by said conductive layer.

5 An envelope structure for a cathode ray tube, comprising:

a hollow funnel member of electrical insulative material having an opening in the larger end thereof;

.a face plate of electrical insulative material;

a seal layer of vitreous electrical insulative material fused directly to the funnel member and joining said face plate to the larger end of said funnel to close the opening in said funnel with a vacuum-tight seal; and

an electrically conductive layer of tin oxide coated over the inner surface of said face plate beneath said seal layer, at least a portion of said conductive layer extending through said seal from the interior to the exterior of said envelope.

7 6. An envelope structure for a cathode ray tube, comprising; i a hollow funnel member of ceramic material having an opening in the larger end thereof; I

-a flat face plate of glass material;

a seallayer of electrical insulative glass fused to the funnel member and joining said face plate to the larger end of said funnel to close the opening in said funnel with a vacuum-tight seal; and

alight transparent, electrically conductive layer of tin oxide coated over the inner surface of said face plate beneath saidseal layer, at least a portionof said conductive layer extending through said seal from the interior to the exterior of said envelope,

7. An envelope structure for a cathode ray tube, comprising:

a hollow funnel member, of. electrical insulative material having an opening in the larger end thereof; a flat'face plate of electrical insulative glass material; a seal layer ofelectrica-l insulative glass rnaterial fused directly to the funnel member and joining said face plate .to the larger end of said funnel to close the opening in said funnel with a vacuumvtightjseal; and a plurality of areas of light transparent, electrical-1y conductive material coated over the inner surface of said face plate-cachet said areas being insulatingly spaced from the other areas and havinga lead por: tion extending beneaththe seal layerthrough said seal to the exterior of said envelope. 8. An envelope structure for a cathode ray prising: i r t a hollow funnel member of ceramic material having a rectangular opening in the larger end thereof; a flat rectangular face plate of glass material;

tube, coma seal layer of electrical insulative glass material joining said face plate to the larger end of said funnel to close the opening in said funnel with a vacuums tight seal'extending around the outer edge of said faceplate; and

a plurality of light transparengelectrically conductive areas of tin oxide coated over the inner-surface of said face plate and insulatingly spaced from each: other, each conductive area having a lead portion; extending beneath said seal layer through said seal;

to the exterior of said envelope.

9. An envelope prising:

.a hollow funnel member of ceramic material having an opening in the larger end thereof; 7

a face plate of glass material;

a seal layerof electrical insulative glass material fused to the funnel-member and joining said face plate to the larger end of said funnel to closethe opening in said. funnel-with a vacuum-tightseal;

a plurality of areas of light transparent, electrically con-- ductive material coated over the innersurface of said face plate, each of said areas being ,insulatingly spaced from the other areas and having a lead portion extending beneath the seal layer through said seal to the exterior of said envelope; and

a plurality of spaced connector strips of electrically conductive material coated on the outer surface of said funnel into. electrical contact with difierent ones of the lead portions of said areas.

References Cited by. the Examiner UNITED STATES ,PATENTS,

2,273,439 2/1942 Freeman -43 2,562,163 7/1951 Niensch et a1. 313-64 2,889,952 6/ 1959' Claypoole 106-53 2,952,499 9/1960 =Carson 65-43 3,061,664 1 0/1962 Kegg 106-53 4 3,113,878 12/1963 Martin 10653 X: 3,136,909 r 6/ 1964 Cope 313-65 3,144,575 8/1964 Babits 313-65 1 3,207,936 I 9/1965 Wilbanks et al 313-283,

' FOREIGN PATENTS 467,296 6/1937 Great Britain. f

JOHN W. HUCKERT, Primary Examiner.

A. I. JAMES, Assistant Examiner,

structure for a cathode ray tube, com- 

9. AN ENVELOPE STRUCTURE FOR A CATHODE RAY TUBE, COMPRISING: A HOLLOW FUNNEL MEMBER OF CERAMIC MATERIAL HAVING AN OPENING IN THE LARGER END THEREOF; A FACE PLATE OF GLASS MATERIAL; A SEAL LAYER OF ELECTRICAL INSULATIVE GLASS MATERIAL FUSED TO THE FUNNEL MEMBER AND JOINING SAID FACE PLATE TO THE LARGER END OF SAID FUNNEL TO CLOSE THE OPENING IN SAID FUNNEL WITH A VACUUM-TIGHT SEAL; A PLURALITY OF AREAS OF LIGHT TRANSPARENT, ELECTRICALLY CONDUCTIVE MATERIAL COATED OVER THE INNER SURFACE OF SAID FACE PLATE, EACH OF SAID AREAS BEING INSULATINGLY SPACED FROM THE OUTER AREAS AND HAVING A LEAD PORTION EXTENDING BENEATH THE SEAL LAYER THROUGH SAID SEAL TO THE EXTERIOR OF SAID ENVELOPE; AND A PLURALITY OF SPACED CONNECTOR STRIPS OF ELECTRICALLY CONDUCTIVE MATERIAL COATED ON THE OUTER SURFACE OF 